As a result of the widespread development of electric powered and hybrid/electric powered vehicles, there is a need for a mechanical and electrical means for terminating shielded power transmission cables at connection points within a vehicle. Electric powered vehicles have been developed to use DC and multiple phase AC electric power systems capable of providing desired levels of electric power to wheel drive motors and powered accessories mounted on vehicles. The connectors must be capable of transmitting the continuous electric current and peak current of the cable. 200-500 amperes is typical for electric vehicle power demands. The conductive core in a shielded power cable is typically composed of stranded and twisted copper or aluminum wire having a total cross-sectional area up to approximately 100 mm2. The outer conductive layer in a shielded power cable is typically a braided metal sheath. The electrical insulation layers need to be mechanically, chemically and thermally robust and stable under harsh conditions.
The connection from the braided sheath to ground in a high power shielded cable must have adequate current carrying capacity. Excessive electrical resistance in the connection will cause resistive heating. Any electric power expended in the form of heat generation due to resistive heating will reduce the efficiency of the electric system, which must be avoided in an electric powered vehicle. In addition, excessive heat generated in the connector can cause corrosion of conductors, melt insulators, deteriorate materials from which the connector is constructed, cause damage to adjacent parts and increase a risk of fire.
Another significant consideration in designing connectors used in electric vehicles is protection of electric/electronic components within the vehicle from electromagnetic interference radiating from power transmission cables. Such protection is provided around the power cable by the conductive braided sheath surrounding the conductive core. For maximum protection, the outer conductor must continue, uninterrupted, around the entire circumference of the conductive core for the entire length of the cable, including at the electrical/mechanical connection points. Gaps or inconsistencies in the outer conductor (braided sheath) at the connector will reduce the shielding capability of the connector. Since electromagnetic interference can induce soft errors in a vehicle's electronic systems, poor protection against such interference in an electric or hybrid/electric vehicle could potentially damage the electronics and computer systems controlling the vehicle and affect the safe operation of the vehicle, putting passengers and others at risk of harm.
To provide a low resistance connection between the connector body and the flexible braided sheath, contact surface area must be maximized in the connector body. Maintaining a high level of shielding against emission of electromagnetic radiation also requires the flexible braided sheath to be distributed as evenly as possible around the circumference of the connection. The surface contacts in the interior of the connector body are of high importance in a connector meeting the above requirements.
Many connectors manufactured by prior art methods (e.g., stamping) have seams that can cause gaps in RF shielding of the transmission path. In addition, the internal surfaces of many connectors made by prior art methods provide inferior quality electrical contact to the braided sheath and a higher resistance electrical path to ground. As a result, connectors of the prior art can produce excessive interference and provide inferior grounding.
In addition to electrical considerations, connectors used inside a vehicle will be subjected to vibrations and other mechanical stresses during vehicle operation. Therefore, a shielded cable connector assembly is needed that can provide sufficient power transmission for the drive motors and accessories of an electric vehicle, provide a secure mechanical connection from the cable to a termination point, protect electrical components from electromagnetic interference generated within the cable, and provide a low resistance connection to ground. The present invention addresses these deficiencies in the prior art.